Prospecting plant growth promoting bacteria and cyanobacteria as options for enrichment of macro- and micronutrients in grains in rice–wheat cropping sequence

The influence of plant growth promoting bacteria (PGPB) and cyanobacteria, alone and in combination, was investigated on micronutrient enrichment and yield in rice–wheat sequence, over a period of two years. Analysis of variance (ANOVA) in both crops indicated significant differences in soil dehydrogenase activity and micronutrient enrichment in grains (Fe, Zn in rice, and Cu, Mn in wheat). The combined inoculation of Anabaena oscillarioides CR3, Brevundimonas diminuta PR7, and Ochrobactrum anthropi PR10 (T6) significantly increased nitrogen, phosphorus, and potassium (NPK) content and improved rice yield by 21.2%, as compared to the application of recommended dose of NPK fertilizers (T2). The treatment T5 (Providencia sp. PR3 + B. diminuta PR7 + O. anthropi PR10) recorded an enhancement of 13–16% in Fe, Zn, Cu, and Mn concentrations, respectively, in rice grains. In wheat, Providencia sp. PW5 (T6) recorded the highest yield (5.23 Mg ha−1) and significantly higher enrichment of Fe and Cu (44–45%) in the grains. This study highlighted the promise of combinations of cyanobacteria/bacteria and their synergistic action in biofortification and providing savings of 40–60 kg N ha−1. Future focus needs to be towards integrating such promising environment-friendly and environmentally sustainable options in nutrient management strategies for this cropping sequence.